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S. Sindhuri et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 4, Issue 4( Version 1), April 2014, pp.426-429
RESEARCH ARTICLE
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Implementation of an Efficient Ripple Carry Adder by Low
Power Techniques for Ultra Applications
S. Sindhuri1, R. Sravani2, S. Rambabu3
Dept of ECE, SREC, Nandyal.
Dept of ECE, SREC, NANDYAL
Asst professor, SREC, Nandyal
ABSTRACT
The main goal of this paper is to provide new low power solutions for very large scale integration. Designers
especially focus on the reduction of the power dissipation which shows increasing growth with the scaling down
of the technologies. In this paper various technologies at the different levels of the design process have been
implemented to reduce the power dissipation at the circuit, architecture and system levels. Previous technologies
are summarized and compared with our new approach is presented in this paper.
The main objective of this project is the reduction of power dissipation by eliminating the PMOS tree
and also by utilizing energy stored at the output can be retrieved by the reversing the current source direction
discharging process instead of dissipation in NMOS network with SDCVSL, ADIABATIC LOGIC. It also
increases the performance of circuits.
Here for this project, I am using MICRO WINDOW TOOL. By using this tool we can develop schematic for all
above techniques and also find out the power dissipation.
Key words: Low power, CMOS, SDCVSL, Adiabatic logic.
I. INTRODUCTION:
Much of the research efforts of the past
years in the area of digital electronics has been
directed towards increasing the speed of digital
systems. Recently, the requirement of portability and
the moderate improvement in battery performance
indicate that the power dissipation is one of the most
critical design parameters.
The three most widely accepted metrics to
measure the quality of a circuit or to compare various
circuit styles are area, delay and power dissipation.
Portability imposes a strict limitation on power
dissipation while still demands high computational
speeds. Hence, in recent VLSI systems the powerdelay product becomes the most essential metric of
performance. The reduction of the power dissipation
and the improvement of the speed require
optimizations at all levels of the design procedure. In
this chapter, the proper circuit style and methodology
is considered. Since, most digital
Circuitry is composed of simple and/or complex
gates, we study the best way to implement adders in
order to achieve low power dissipation and high
speed.
Several circuit design techniques are
compared in order to find their efficiency in terms of
speed and power dissipation. A review of the existing
CMOS circuit design styles is given, describing their
advantages and their limitations. Furthermore, a fourbit ripple carry adder for use as a benchmark circuit
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was designed in a full-custom manner by using the
different design styles, and detailed transistor-level
simulations using HSPICE [2] were performed. Also,
various designs and implementations of four
multipliers are analysed in the terms of delay and
power consumption. Two ways of power
measurements are used.
In this chapter we study two different
CMOS logic styles, they are
i. STATIC DIFFERENTIAL CASCODE
VOLTAGE SWITCH(SDCVSL)
ii. ADIABATIC LOGIC
Here we are comparing the parameters like
power, delay and area of the above mentioned
techniques with the CONVENTIONAL CMOS
technique.
II. Power and Delay in Conventional
CMOS Circuits:
Since the objective is to investigate the
tradeoffs that are possible at the circuit level in order
to reduce power dissipation while maintaining the
overall system throughput, we must first study the
parameters that affect the power dissipation and the
speed of a circuit. It is well known that one of the
major advantage of CMOS circuits over single
polarity MOS circuits, is that the static power
dissipation is very small and limited to leakage.
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S. Sindhuri et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 4, Issue 4( Version 1), April 2014, pp.426-429
However, in some cases such as bias circuitry and
pseudo-nMOS logic, static power is dissipated.
Considering that in CMOS circuits the leakage
current between the diffusion regions and the
substrate is negligible, the two major sources of
power dissipation are the switching and the shortcircuit power dissipation
Where
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SDCVSL CARRY
f is the node transition activity factor,
is the load capacitance,
is the supply
voltage,
f is the switching frequency,
is the
current which arises when a direct path from power
supply to ground is caused, for a short period of time
during low to high or high to low node transitions .
The switching component of power arises when
energy is drawn from the power supply to charge
parasitic capacitors. It is the dominant power
component in a well designed circuit and it can be
lowered by reducing one or more of pf , CL, Vdd and
f, while retaining the required speed and
functionality.
Even though the exact analysis of circuit
delay is quite complex, a simple first-order derivation
can be used in order to show its dependency of the
circuit parameters
This carry circuit of SDCVSL circuit consists of
12 transistors with 3 inputs.
SDCVSL SUM
III. Static Differential Cascode Voltage
Switch :
Static
DCVSL is a differential style of
logic requiring both true and complementary Signals
to be routed to gates. Figure 5.4 shows the circuit
diagram of the static DCVSL full adder. Two
complementary NMOSFET switching trees are
constructed to a pair of cross-coupled PMOSFET
transistors.
Depending on the differential inputs one of
the outputs is pulled down by the corresponding
NMOSFET network. The differential output is then
latched by the cross-coupled PMOSFET transistors.
Since the inputs drive only the NMOSFET transistors
of the switching trees, the input capacitance is
typically two or three times smaller than that of the
conventional static CMOS logic.
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SDCVSL FULL ADDER
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S. Sindhuri et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 4, Issue 4( Version 1), April 2014, pp.426-429
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IV. ADIABATIC LOGIC:
The operation of adiabatic logic gate is
divided into two distinct stages: one stage is
used for logic evaluation; the other stage is used to
reset the gate output logic value.
1. Conventional Switching
There are three major sources of power
dissipation in digital CMOS circuits those are
dynamic, short circuit and leakage power dissipation.
The dominant component is dynamic
power dissipation and is due to charging, discharging
of load capacitance.
2. Adiabatic Switching
Adiabatic switching can be achieved by
ensuring that the potential across the switching
devices is kept arbitrarily small. This can be achieved
by charging the capacitor from time varying voltage
source or constant current source.
In literature, adiabatic logic circuits
classified into two types: full adiabatic and quasi or
partial adiabatic circuits. Full-adiabatic circuits have
no non-adiabatic loss, but they are much more
complex than quasi-adiabatic circuits. Quasiadiabatic circuits have simple architecture and power
clock system. There are two types of energy loss in
quasi-adiabatic circuits, adiabatic loss and
nonadiabatic loss. The adiabatic loss occurs when
current flows through non-ideal switch, which is
proportional to the frequency of the power-clock.
If any voltage difference between the two
terminals of a switch exists when it is turned on, nonadiabatic loss occurs. The non-adiabatic loss, which
is independent of the frequency of the power-clock, is
proportional to the node capacitance and the square
of the voltage difference. Several quasi-adiabatic
logic architectures have been reported, such as
ECRL, 2N-2N-2P, PFAL.
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ADIABATIC FULL ADDER
USING PASS TRANSISTOR
Technique power
Area
Delay
CMOS
SDCVSL
Adiabatic
18ps
0.94ns
8.88ns
16.969uw
0.164mw
7.037uw
62*12um
42*13um
16*13um
From the above analysis, we came to know
that adiabatic logic is the best technique. So we
design ripple carry adder using the adiabatic
technique because it consumes less power.
Ripple carry adder by using adiabatic logic:
Above ripple carry adder is designed by
using adiabatic full adder. It consists of four full
adders. This ripple carry adder consumes less power
as adiabatic logic technique is the efficient in
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S. Sindhuri et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 4, Issue 4( Version 1), April 2014, pp.426-429
consuming less
dissipation.
power
and
reducing
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power
V. CONCLUSION
In this chapter, the most common kinds of
adders have been characterized in terms of power,
using either a traditional low-level design flow
paradigm, which is rather tedious and incompatible
with modern design flows, but provides the most
accurate results, or a high-level design flow
paradigm, which is commonly used.
In this paper we compared the performance
of SDCVSL and adiabatic logic adder circuits with
traditional CMOS adder circuits. The analysis shows
that designs based on adiabatic principle gives
superior performance when compared to traditional
approaches in terms of power even though their
transistor count is high in some circuits so for low
power and ultra low power requirements adiabatic
logic is an effective alternative for traditional CMOS
logic circuit design.
A four-bit ripple carry adder was designed
using adiabatic logic here is used as the benchmark
circuit. All the circuits have been designed in a fullcustom manner.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
A. Chandrakasan, R. Brodersen, Low Power
Digital
Design,
Kluwer
Academic
Publishers, 1995.
Meta-Software, HSPICE User’s Manual Version 96.1,1996.
K. Yano, Y. Sasaki, K. Rikino, K. Seki,
“Top-Down Pass-Transistor Logic Design”.
IEEE Journal of Solid-State Circuits, vol.31,
pp. 792-803. 1996
MIPS
Technologies,
“R4200
Microprocessor Product Information”, MIPS
Technologies Inc., 1994
R K. Navi, Md.Reza Saatchi and O. Daei,
(2009) “A High-Speed Hybrid Full Adder,”
European Journal of Scientific Research,Vol
26 No.1,pp 29-33.
D. Sourdis, C. Piguet and C. Goutis,(2002) “
Designing CMOS Circuits for Low Power,
European
Low-Power
Initiative
for
Electronic System Design”, Reading pp 7196, Kluwer Academic Publishers.
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